Feasibility analysis of modified pedicle subtraction osteotomy for cervical 7 by evaluating radiographic results

Objective To illustrate the prospects of osteotomy for severe cervicothoracic kyphosis in single segment via posterior approach by exploring the feasibility of modified pedicle subtraction osteotomy(PSO) technique for the C₇ by evaluating radiographic results of healthy volunteers. Methods A retrospective study on radiographic data of CT two-dimensional reconstruction on healthy volunteers in our hospital from 2012-2015 was conducted.On the sagittal plane,we simulate osteotomy with PSO technique and document the angle of osteotomy and the necessary excision length of facet joints in adjacent segments.Pre-judge whether the C₇ and C₈ nerve roots would be compressed or not by calculating the distance between C₆ pedicle and T₁ pedicle;Pre-judge whether the pedicles of adjacent segments would be damaged by researching the relationship between oteotomy line and C₆,T₁ pedicles.And we use this result to illustrate the theoretical feasibility of modified PSO technique. Results A total of 100 healthy cervical CT reconstruction imaging data was included in the study.We measured that the modified PSO technique can improve the angle with(60.0±6.2)mm and (4.7±2.1)mm of C₆ inferior facet and (6.5±2.6)mm of T₁ superior facet need resection during the surgery.The results of simulating osteotomy show that the ratio of C₇ and C₈ nerve compression after osteotomy was 74%,and the ratio of adjacent vertebral segment pedicle without injury after complete osteotomy was 82%.Theoretically,the feasible ratio of osteotomy was 68%. Conclusion The radiographic measurements conclude that the modified PSO technique for C₇ segment is feasible，and it may a promising method for severe cervicothoracic kyphosis.